From: Lasse Collin <lasse.collin@tukaani.org>
Date: Fri, 11 Nov 2011 13:34:24 +0000 (+0100)
Subject: Decompressors: validate match distance in unlzma.c
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=24bde2170dde6ed1a4a3de7c96a019eb4dae9501;p=xen.git

Decompressors: validate match distance in unlzma.c

From: Lasse Collin <lasse.collin@tukaani.org>

Validate the newly decoded distance (rep0) in process_bit1().  This is to
detect corrupt LZMA data quickly.  The old code can run for long time
producing garbage until it hits the end of the input.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
Committed-by: Jan Beulich <jbeulich@suse.com>
---

diff --git a/xen/common/unlzma.c b/xen/common/unlzma.c
index 6dcd7ba20b..87b9e0a964 100644
--- a/xen/common/unlzma.c
+++ b/xen/common/unlzma.c
@@ -516,6 +516,9 @@ static inline int INIT process_bit1(struct writer *wr, struct rc *rc,
 			cst->rep0 = pos_slot;
 		if (++(cst->rep0) == 0)
 			return 0;
+		if (cst->rep0 > wr->header->dict_size
+				|| cst->rep0 > get_pos(wr))
+			return -1;
 	}
 
 	len += LZMA_MATCH_MIN_LEN;